Indirect Exam 1 Flashcards
Describe an optimal restoration
Combo of biologic, mechanical, and esthetic properties
Which property?
Retention form
Mechanical
Which property?
Resistance form
Mechanical
Which property?
Deformation
Mechanical
Which property?
Conservation of tooth structure
Biologic
Which property?
Avoidance of overcontouring
Biologic
Which property?
Supragingival margins
Biologic
Which property?
Harmonious occlusion
Biologic
Which property?
Protection against tooth fracture
Biologic
Which property?
Minimum display of metal
Esthetic
Which property?
Max thickness of porcelain
Esthetic
Which property?
Porcelain occlusal surfaces
Esthetic
Which property?
Subgingival margins
Esthetic
Name 3 biological considerations
Adjacent teeth
Soft tissue
Pulp
How can soft tissue damage be prevented?
Retraction with aspirator tip, mirror, or isolite
What are 4 biological considerations in regards to the pulp?
Pulp size
Temp
Chemical action
Bacterial action
Name the 6 ways we can conserve tooth structure
- Partial coverage rather than complete coverage
- Prep of teeth with minimum practical convergence angle (taper) btwn axial walls
- Prep occlusal surface so reduction follows anatomical planes (gives uniform thickness to restoration)
- Prep axial surfaces so tooth structure is removed evenly
- Select conservative margin compatible with other principles of tooth prep
- Avoid unnecessary apical extension
The more apical the margin (subgingival), the __________ (more/less) conservative
less
What are the 4 types of crown materials?
PFM
PFZ
Monolithic ceramic
Full metal
Margin = ?
Finish line
What are the types of margin designs?
Bevel
Chamfer
Shoulder
Feather-edge
Which type of margin?
Advantages:
Removes unsupported enamel
Allows finishing of metal
Bevel margin
Which type of margin?
Disadvantage:
Can extend prep into sulcus
Bevel margin
Which type of margin?
Indications:
Facial margin of maxillary partial-coverage restorations
Inlay/onlay margins
Bevel margin
Which type of margin?
Advantages:
Fewer complications
Adequate bulk
Chamfer margin
Which type of margin?
Disadvantage:
J-lip
Chamfer margin
Which type of margin?
Indications:
Full metal, PFM, and some ceramics
Chamfer margin
Which type of margin?
Advantage:
Bulk of restorative material
Shoulder margin
Which type of margin?
Disadvantage:
Less conservative
Shoulder margin
Which type of margin?
Indications:
Facial margin of PFM crowns
All ceramic crowns
Shoulder margin
Which type of margin?
Advantage:
Conservative prep
Feather-edge margin
Which type of margin?
Disadvantages:
Not sufficient bulk
Requires metal margin
Feather-edge margin
Which type of margin?
Indication:
Long preps
Feather-edge margin
What are the 3 possible margin placements?
Supragingival
Epigingival
Subgingival
Which margin placement?
Easily finished, easily kept clean
Supragingival
Which margin placement?
Impressions easier to get without damaging soft tissue
Supragingival
Which margin placement?
Restorations can be easily evaluated at recall appts
Supragingival
Which margin placement?
Not ideal, places interface tooth/restoration right on gingival crest
Epigingival
Which margin placement?
Can create inflammation and gingivitis
Epigingival
Which margin placement?
More esthetic
Subgingival
Which margin placement?
Provides additional crown retention
Subgingival
Which margin placement?
Root sensitivity
Subgingival
Which margin placement?
Not indicated in pts with caries, erosion, subgingival restorations, and crown lengthenings
Subgingival
What are the occlusal considerations mentioned in lecture?
Rollercoaster
Supraerupted
Occlusal trauma
Titlted teeth
Feature of a tooth prep that resists dislodgement of a crown in a vertical direction or along path of placement
Retention form
Features of a tooth prep that enhance stability of a restoration and resist dislodgement along an axis other than the path of placement
Resistance form
Why should you prep with a green or black label diamond with heavy grit?
The rougher the surface better
Which gold alloys are used for intracoronal cast restorations?
Type I and II
Which gold alloys are used for crowns and FDPs?
Type III and IV
The thicker the cement, the __________ (stronger/weaker) the strength
weaker
The higher the SA, the _____________ (better/worse) the retention
better
The higher the axial walls, the ___________ (higher/lower) the SA
higher
The wider the prepped tooth, the ___________ (higher/lower) the SA
higher
What can cause a crown to dislodge?
Sticky food like caramel
What should be the degree of convergence of your prep?
6-10 degrees
Reduces stress on remaining tooth structure
Rounded internal line angles (no sharp edges!)
What is the ideal vs acceptable taper?
Ideal = 6-10 degrees
Acceptable = 10-20 degrees
How can you improve the resistance and retention of a crown in the case of a virgin tooth?
6-10 degree convergence
Conservative prep
Lower margins to have longer axial walls
What material can you use to improve the resistance and retention of a crown?
Stronger cement (ex: Panavia, a resin cement)
How can you improve the resistance and retention of a crown in the case of replacing or prepping a tooth that already has lost significant structure?
Retentive grooves
Prepare wider margin to reduce convergence
Build-up with pins
Long narrow channel or depression, such as indentation btwn tooth cusps or retentive features placed on tooth surfaces to augment the retentive characteristics of crown preps
Groove
A mesial and distal groove helps protect from what type of dislodgement?
Bucco-lingual dislodgement
A buccal and lingual groove helps protect from what type of dislodgement?
Mesio-distal dislodgement
What are the 7 key principles of preps?
Conservation of tooth structure
Resistance form
Retention form
Structural durability
Marginal integrity
Preservation of the periodontium
Aesthetic considerations
Which key principle of preps?
To avoid weakening tooth unnecessarily
Conservation of tooth structure
Which key principle of preps?
To avoid compromising the pulp
Conservation of tooth structure
Which key principle of preps?
To prevent dislodgment of a cemented restoration by apical or obliquely-directed forces
Resistance form
Which key principle of preps?
To prevent displacement of a cemented restoration along any of its paths of insertion, including long axis of the prep
Retention form
Which key principle of preps?
To provide enough space for a crown that is sufficiently thick to prevent fracture, distortion, or perforation
Structural durability
Which key principle of preps?
To prepare a finish line to accommodate a robust margin with close adaptation to minimize microleakage
Marginal integrity
Which key principle of preps?
To shape the prep so the crown is not over-contoured and its margin is accessible for optimal oral hygiene
Preservation of periodontium
Which key principle of preps?
To create enough space for aesthetic veneers where indicated
Aesthetic considerations
Specific direction in which a prosthesis is placed on the abutment teeth or implant
Path of placement/insertion/withdrawal
When visualizing the path of placement, how should you look at the center of the occlusal surface of your prep?
With 1 eye closed
What should be seen from the ideal path of insertion?
Prepped tooth
The path of placement helps to ensure the prep is not ____________ or _______________
undercut; overtapered
When visualizing the path of placement, what should be able to be seen at 360 degrees?
Margin (finish line)
When using indirect vision to visualize the path of placement, when should you stop maneuvering the mirror?
When prep is centered
What is the path of placement for posterior teeth?
Perpendicular to occlusal plane
What is the path of placement for maxillary posterior teeth?
Slightly buccal
What is the path of placement for mandibular posterior teeth?
Slightly lingual
What is the path of placement for anterior teeth?
Flared to facial, finding a mid-point btwn the abutment’s tooth axis
What classification of dental alloy?
Type I
Inlays
What classification of dental alloy?
Type II
Onlays
What classification of dental alloy?
Type III
Crowns/FDPs
What classification of dental alloy?
Type IV
RPDs
Type I hardness
Soft
Type II hardness
Medium
Type III hardness
Hard
Type IV hardness
Extra hard
What type of dental alloy?
PFM and Full Metal crowns
Type III
7 requirements for PFM crowns
High fusion temp to withstand porcelain firing
Thermal coefficient of expansion > than porcelain
Promote durable metal/porcelain bond
High mechanical properties
Biocompatible
Tarnish resistance
Usually nickel free
What are the available alloy systems?
Noble metal alloys
Base metal alloys
Which noble metal alloys are corrosion resistant?
Gold-based
Palladium-based
What does corrosion resistant mean?
Do not form stable oxides
Which metals oxidize to form a chromium oxide surface layer?
Base metals
Which alloy system is stronger: noble metal or base metal?
Base metal alloys
What are the main elements in base metal alloys?
Nickel and Cobalt
When base metals oxidize to form a chromium oxide surface layer, what is blocked? What does this prevent?
Blocks diffusion of oxygen
Prevents corrosion of underlying metal
What are the 3 main noble metals?
Gold (Au)
Platinum (Pt)
Palladium (Pd)
Which metal alloy?
60% noble metals
At least 40% gold
High noble metal alloy
Original PFM alloy (98% nobel metal)
Gold-Platinum-Palladium
First low-gold alternative alloy (50%)
Gold-Palladium-Silver
What improves the castability in the first low-gold alternative alloy?
Silver
Very popular noble metal alloy, has excellent mechanical properties
Palladium-Silver
Which metal alloy?
25% noble metals
No gold requirement
Noble metal alloy
What are the 3 options/combinations for noble metal alloy?
Palladium-Silver
Palladium-Copper-Ga
Palladium-Ga
Which noble metal alloy has 0-2% gold and 30-35% silver?
Palladium-Silver
Which noble metal alloy has at least 70% palladium?
Palladium-Copper-Ga
Which noble metal alloy is a dark oxide that is more difficult to mask, making it not very popular?
Palladium-Ga
What are the 4 options/combinations for base metal alloy?
Nickel-Cr
Be
Nickel
Cobalt-Cr
Which base metal alloy?
Not as burnishable as noble metals (gold, platinum, palladium)
Nickel-Cr
Which base metal alloy?
High modulus of elasticity, ideal for long-span FDPs
Nickel-Cr
Which base metal alloy?
Lower melting point and improves castability
Be
Which base metal alloy?
Toxic; associated with lung and nasal cancer
Nickel
Which base metal alloy?
9% of females are allergic
Nickel
Which base metal alloy?
0.9% of males are allergic
Nickel
Which base metal alloy?
No potential health problems
Co-Cr
Which base metal alloy?
Highest modulus of elasticity
Co-Cr
Which base metal alloy?
Finishing is very difficult
Co-Cr
Which base metal alloy?
High level of hardness
Co-Cr
Due to new advances of digital tech, many of today’s crowns are made with which alloy?
Co-Cr
What technique are Co-Cr alloys printed with?
Selective Laser Melting technique (SLM)
What are PFM and full metal crowns used for?
Single crowns
FDPs (1 or 2 pontics)
If cement films are < than ______ um, then a successful restoration is possible
120
What are the 4 theories of the porcelain/metal attachment mechanism?
Chemical bonding
Compression bonding
Mechanical retention
Van der waals forces (secondary)
The attraction btwn charged atoms that are in intimate contact, yet do not actually exchange electrons
Van der waals forces (secondary)
How are Van der waals forces (secondary) different from chemical bonding (primary)?
There is sharing/exchange of electrons in chemical bonding
The _________ (worse/better) the wetting of the metal surface w/ the liquid porcelain, the greater the Van der waals forces
better
Are Van der waals forces strong or weak?
Weak
How is mechanical retention achieved in metal casting?
Metal cast has microscopic irregularities;
Opaque porcelain flows into irregularities when fired
What kind of surface can porcelain fuse to?
Polished surfaces
T/F: Porcelain does not require a roughened surface to bond to metal, since it can fuse to polished surfaces
True
Air abrasion enhances mechanical retention surface irregularities (stress concentrations) while increasing the overall SA available for bonding
Aluminum oxide
What is porcelain strongest under?
Compression
What is porcelain weakest under?
Tension
If thermal expansion of the metal substructure is greater than that of the porcelain placed over it, the porcelain will ____________ during cooling
compress
When cooling a restoration, the metal contracts _________ (less/more) than the porcelain
more
The difference in contraction rates creates ___________ forces on metal and ______________ forces on porcelain
tensile; compressive
Without a wraparound effect in a full PFM crown, there is _________ (less/more) likelihood that this compression bonding will develop
less
Most significant mechanism
Chemical bonding
Describe the chemical bonding that happens in a crown
Porcelain bonds to oxides of metal substructure
What are the 2 hypotheses of chemical bonding?
Oxide layer bonds to metal on one side and porcelain on other side (grilled cheese)
Metal oxides are dissolved by opaque porcelain layer (2 pieces of bread on top of each other)
In chemical bonding, both covalent and ionic bonds are thought to form, but only a _______________ layer of oxides is believed to be required for chemical bonding to occur
monomolecular (single)
Describe steps of placing opaque porcelain on metal
- Opaque powder mixed w/ distilled water
- Thin wash layer applied w/ brush
- Coping dried & fired under vacuum
- 2nd opaque layer applied to mask the metal
- Coping gently vibrated to condense porcelain & remove excess water
Opaque layer of porcelain should be as ________ as possible, approximately _____ mm thick
thin; 0.3 mm
What type of crown?
Indicated for surveyed crown (RDP), malocclusion, FDP, endo
PFM
FMC
What type of crown?
Indicated when there’s a loss of dental structure
PFM
What type of crown?
Indicated for esthetics
PFM
All ceramic
What type of crown?
When a more conservative restoration is a reliable option
PFM
FMC
What type of crown?
Contraindicated for active caries and perio
PFM
FMC
What type of crown?
Contraindicated for young patients and pulp exposure
PFM
FMC (not as critical as PFM tho)
What type of crown?
Contraindicated when esthetics are an issue
FMC
What type of crown?
Advantage = strong, helps integrity of tooth (compared to onlays/inlays)
PFM
What type of crown?
Advantage = esthetics (compared to full metal)
PFM
All ceramic
What type of crown?
Advantage = permits correction of axial form for RDP tx
PFM
FMC
What type of crown?
Disadvantage = increased removal of dental structure compared to onlays/inlays
PFM (more than FMC)
FMC
What type of crown?
Subgingival margin on anterior segment to achieve esthetics; risk for perio
PFM
How many mm is the metal coping and porcelain on axial wall for PFM crown?
Metal coping = 0.3 mm
Porcelain = 1-1.2 mm
How many mm is the metal coping and porcelain on incisal edge for PFM crown?
Metal coping = 0.3 mm
Porcelain = 1.2-1.7 mm
What does a metal occlusion on a PFM crown allow for?
More conservative prep (as thin as 1 mm)
Stronger occlusal surface (ex: pt with bruxism)
When is a metal occlusion on a PFM crown indicated?
Limited interocclusal clearance
What is one downfall of a metal occlusion on a PFM crown?
Poor esthetics